Method including producing a monocrystalline layer

ABSTRACT

A method including producing a monocrystalline layer is disclosed. A first lattice constant on a monocrystalline substrate has a second lattice constant at least in a near-surface region. The second lattice constant is different from the first lattice constant. Lattice matching atoms are implanted into the near-surface region. The near-surface region is momentarily melted. A layer is epitaxially deposited on the near-surface region that has solidified in monocrystalline fashion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Utility Patent Application claims priority to German PatentApplication No. DE 10 2008 032 171.0 filed on Jul. 8, 2008, which isincorporated herein by reference.

BACKGROUND

The invention relates to a method for producing a monocrystalline layeron a substrate. In one embodiment, the invention relates to a method forproducing a semiconductor including a monocrystalline layer on asubstrate.

Monocrystalline layers can be produced by epitaxial deposition on amonocrystalline substrate. In this case, different lattice constants ofthe layer and of the substrate can lead to defects in the crystallattice of the layer. For these and other reasons, there is a need forthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIGS. 1 a to 1 c illustrate in schematic cross-sectional views selectedmethod processes of one embodiment of a method including producing amonocrystalline layer on a substrate.

FIG. 2 schematically illustrates an excerpt from a crystal lattice atthe transition from a substrate to a monocrystalline layer in accordancewith one embodiment.

FIG. 3 schematically illustrates an excerpt from a crystal lattice atthe transition from a substrate to a monocrystalline layer in accordancewith one embodiment.

FIG. 4 schematically illustrates an excerpt from a crystal lattice atthe transition from a substrate to a monocrystalline layer in accordancewith one embodiment.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

It is to be understood that the features of the various exemplaryembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

Exemplary embodiments are explained in more detail below with referenceto the accompanying Figures.

However, the invention is not restricted to the embodiments specificallydescribed, but rather can be modified and altered in a suitable manner.It lies within the scope of the invention to suitably combine individualfeatures and feature combinations of one embodiment with features andfeature combinations of another embodiment in order to obtain furtherembodiments according to the invention.

Before the exemplary embodiments of the present invention are explainedin more detail below with reference to the Figures, it is pointed outthat identical elements in the Figures are provided with the same orsimilar reference symbols and that a repeated description of theseelements is omitted. Furthermore, the Figures are not necessarily trueto scale; rather, the main emphasis is on elucidating the basicprinciple.

One embodiment provides a method by which a monocrystalline layer can beproduced as far as possible without any defects on a monocrystallinesubstrate having a different lattice constant.

One embodiment describes a method for producing a monocrystalline layerhaving a first lattice constant on a monocrystalline substrate having asecond lattice constant at least in a near-surface region, the secondlattice constant being different from the first lattice constant,wherein lattice matching atoms are implanted at least in thenear-surface region, the near-surface region is momentarily melted, andthe layer is epitaxially deposited on the near-surface region that hassolidified in monocrystalline fashion.

By using the lattice matching atoms, the lattice constant of thesubstrate can be matched to the lattice constant of the layer to bedeposited thereon. Consequently, during the epitaxial deposition of thelayer on the substrate treated in this way, at least significantly fewerdefects are produced in the layer.

FIG. 1 a illustrates a selected method process for producing amonocrystalline layer on a monocrystalline substrate. In thisembodiment, lattice matching atoms 12 are implanted into amonocrystalline substrate 10 in a near-surface region 11. Thisimplantation process is illustrated with the aid of arrows 14 in FIG. 1a. Suitable implantation doses of the lattice matching atoms 12 lie forexample in the range of 1×10¹⁵ cm⁻² to 1×10¹⁶ cm⁻². The substrate 10 hasa specific lattice constant b before the implantation at least in thenear-surface region 11. The substrate 10 can be for example asemiconductor substrate produced from semiconductor material. All knownsemiconductors such as, for example, germanium, indium phosphide,silicon carbide, gallium arsenide and in one embodiment silicon areappropriate as the semiconductor material.

After the implantation 14 of lattice matching atoms 12 into thenear-surface region 11, the near-surface region 11 is momentarilymelted. In this embodiment, the melting is indicated with the aid ofwavy lines 15 in FIG. 1 b. The melting 15 can be effected for example byusing laser irradiation, in one embodiment by using a pulsed laserirradiation. Depending on the wavelength, laser energy and possibly thenumber of pulses of the laser irradiation, typically a layer having adepth of 0.3 μm to 1 μm is melted at the surface of the substrate 10.During the recrystallization of the melted near-surface region 11, thelattice matching atoms 12 are incorporated for example into the crystallattice of the near-surface region 11 at regular lattice sites, whichleads to a distortion of the original crystal lattice and thus to areduction or increase in the lattice constant b, depending on which typeof lattice matching atoms is used. In this embodiment, the latticematching atoms 12 are chosen with respect to the lattice constant a ofthe layer 13 to be deposited on the near-surface region 11. Such a layer13 produced on the near-surface region 11 that has solidified inmonocrystalline fashion is illustrated schematically in FIG. 1 c. Thelayer 13 can be produced for example with a semiconductor material, inone embodiment silicon. If the lattice constant a of the layer 13 isgreater than the lattice constant b of the substrate 10 or at least ofthe near-surface region 11 of the substrate 10, then lattice matchingatoms 12 that increase this original lattice constant b are chosen. Ifthe lattice constant a of the layer 13 is less than the lattice constantb of the substrate 10 or at least of the near-surface region 11, thenlattice matching atoms 12 that decrease this original lattice constant bare chosen. What can also have an advantageous effect in the case of thevariants described above is that possible crystal defects that arise inthe substrate 10 can be detained by the distortion of the lattice onaccount of the lattice matching atoms.

FIG. 2 illustrates a greatly enlarged excerpt A from FIG. 1 c. In thisembodiment, FIG. 2 schematically illustrates an atomic lattice at thetransition from the substrate 10 to the layer 13. In this embodiment,the substrate 10 has an atomic lattice having a lattice constant b. Thesubstrate 10 is composed e.g., of a material of a first atomic type. Theatoms 20, represented as squares in FIG. 2, of the substrate 10 arearranged at regular lattice sites in the schematic lattice. In thenear-surface region 11 of the substrate 10, lattice matching atoms 12,represented as crosses in FIG. 2, are incorporated into the lattice atregular lattice sites. In this embodiment, the lattice matching atoms 12cause a distortion of the original lattice of the substrate 10 in theform that the original lattice constant b of the substrate 10 isdecreased in the near-surface region 11 provided with lattice matchingatoms 12. As a result of the distortion of the original lattice of thesubstrate 10 in the near-surface region 11 provided with latticematching atoms 12, dislocations 22 can also occur in the crystal latticeof the substrate 10. As a result, the surface 16 of the substrate 10 hasat least approximately a lattice having a lattice constant a. The layer13 produced on the surface 16 of the substrate 10 with atoms 21,represented as circles in FIG. 2, likewise has the lattice constant a.As a result of the matching of the lattice constant b of the substrate10 to the lattice constant a of the layer 13 with the aid of the latticematching atoms 12, epitaxial growth of the layer 13 on the surface 16 ofthe substrate 10 is possible without any defects or at least with fewerdefects than if no lattice matching had taken place between thesubstrate 10 and the layer 13.

FIG. 3 illustrates the greatly enlarged excerpt A from FIG. 1 c ofanother embodiment. This embodiment differs from the embodimentillustrated in FIG. 2 in that the lattice constant b of the substrate 10is less than the lattice constant a of the layer 13 produced on thesubstrate 10. In this case, the lattice matching atoms 12 distort thelattice of the substrate 10 in the near-surface region 11 in the formthat the original lattice constant b of the substrate 10 is increased inthe near-surface region 11. As a result, the surface 16 of the substrate10 likewise has at least approximately the lattice constant a.Therefore, as already explained with regard to FIG. 2, an epitaxialdeposition of the layer 13 is possible at least with a lower defectdensity than in the case of no lattice matching.

FIG. 4 illustrates the enlarged excerpt A from FIG. 1 c in a furtherembodiment. In this embodiment, the substrate 10 also includes in itsoriginal composition alongside the atoms 20, represented as squares inFIG. 4, in addition a further impurity 17, represented as triangles inFIG. 4. A silicon substrate having a dopant such as, for example,phosphorus as impurity 17 shall be mentioned here by way of example. Thelattice of the substrate 10 composed of the atoms 20 and the impurity 17has a lattice constant b. This lattice constant b differs from thelattice constant of a lattice which is constructed only from atoms 20,for example. The lattice constant b is significantly alteredparticularly at high concentrations of the impurity 17. One or moreembodiments provide for example impurity concentrations of at least5×10¹⁹ cm⁻³, in one embodiment even more than 1×10²⁰ cm⁻³, in thesubstrate. In the embodiment illustrated in FIG. 4, a layer 13 composedonly of atoms 20, for example, is produced on the surface 16 of thesubstrate 10. In this embodiment, the lattice of the layer 13 has alattice constant a that is greater than the lattice constant b of thesubstrate 10 composed of atoms 20 and the impurity 17.

In order to match the lattice constant b of the substrate 10 altered bythe impurity 17 to the lattice constant a of the layer 13 composed onlyof atoms 20, lattice matching atoms 12 are therefore at leastincorporated again in the near-surface region 11 of the substrate 10. Asa result of this incorporation of the lattice matching atoms 12, thealteration of the lattice constant b of the substrate caused by theimpurity 17 is compensated for and the lattice constant of thenear-surface region 11 of the substrate 10 is matched to the latticeconstant a of the layer 13. In the above-described case of a siliconsubstrate with phosphorus doping as impurity 17, germanium, for example,is appropriate as lattice matching atom 12. In this embodiment, suitableconcentration ratios Ge:P of germanium atoms to phosphorus atoms can liein the range of between 0.5 and 2, in one embodiment between 1 and 1.5,in order to achieve a sufficient matching of the lattice constant b to asilicon layer 13 produced on such a substrate 10.

One embodiment provides for a non-melting thermal process to be carriedout at the substrate 10 after the melting 15 of the near-surface region11. Such a non-melting thermal process can be for example an RTA (rapidthermal annealing) or a conventional high-temperature process whichleads to a greater expansion of the near-surface region 11 provided withlattice matching atoms 12 into the substrate 10. This diffusion processcan result in a gradient in the concentration profile of the latticematching atoms 12 in the depth of the substrate 10. As a result, it ispossible to produce a continuous transition between the momentarilymelted near-surface region 11 provided with lattice matching atoms 12and the region of the substrate 10 that is not provided with latticematching atoms 12. This fosters the avoidance or at least a furtherreduction of stresses in the epitaxially deposited layer 13. In afurther embodiment, the implantation dose of the lattice matching atoms12 can be correspondingly matched to the increased penetration depth ofthe lattice matching atoms 12, such that in the given case of anadditional impurity 17 in the substrate 10, it is possible to complywith a targeted ratio of impurity 17 to lattice matching atoms 12 atleast in the near-surface region.

In one embodiment, the non-melting thermal process takes place after theepitaxial deposition of the layer 13. As a result, the lattice matchingatoms 12 can also be indiffused into the layer 13.

Another embodiment provides for the non-melting thermal process alreadyto take place before the epitaxial deposition of the layer 13. For thispurpose, before the thermal process, a barrier layer (not illustrated)can be produced on the near-surface region 11 in order as far possibleto avoid outdiffusion of the lattice matching atoms 12 from thenear-surface region 11. An oxide layer, for example, is appropriate asthe barrier layer. The barrier layer is removed again after the thermalprocess.

A further embodiment provides for the implantation 14 of the latticematching atoms 12, the momentary melting 15 of the near-surface region11 and the epitaxial deposition of the layer 13 on the near-surfaceregion 11 that has solidified in monocrystalline fashion to be repeatedonce or a number of times. It is thereby possible to produce a widertransition region with lattice matching atoms 12 with correspondinglattice distortions between the crystal lattice having the latticeconstant a and the crystal lattice having the lattice constant b.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A method comprising: providing a monocrystalline substrate; andproducing a monocrystalline layer having a first lattice constant a onthe monocrystalline substrate having a second lattice constant b atleast in a near-surface region, the second lattice constant beingdifferent from the first lattice constant a, comprising: implantinglattice matching atoms at least in the near-surface region; momentarymelting of the near-surface region; and epitaxial deposition of thelayer on the near-surface region that has solidified in monocrystallinefashion.
 2. The method of claim 1, comprising producing the substratewith a semiconductor material.
 3. The method of claim 2, comprisingwherein the semiconductor material is silicon.
 4. The method of claim 1,comprising wherein the substrate has an impurity.
 5. The method of claim4, comprising wherein the impurity is contained with a concentration ofat least 5×1019 cm-3 in the substrate.
 6. The method of claim 5,comprising wherein the concentration of the impurity is higher than1×1020 cm-3.
 7. The method of claim 3, comprising wherein the impurityis phosphorus.
 8. The method of claim 1, comprising wherein the latticematching atoms are germanium atoms.
 9. The method of claim 7, comprisingwherein a ratio Ge:P of the concentrations between germanium andphosphorus lies in a range of between 0.5 and
 2. 10. The method of claim9, comprising wherein the ratio Ge:P lies between 1 and 1.5.
 11. Amethod comprising: providing a monocrystalline substrate; and producinga monocrystalline layer having a first lattice constant a on themonocrystalline substrate having a second lattice constant b at least ina near-surface region, the second lattice constant being different fromthe first lattice constant a, comprising: implanting lattice matchingatoms at least in the near-surface region; momentary melting of thenear-surface region; and epitaxial deposition of the layer on thenear-surface region that has solidified in monocrystalline fashion,wherein the lattice matching atoms, at least in the near-surface region,match the second lattice constant b to the first lattice constant a bythe lattice matching atoms being incorporated into the crystal latticeof the near-surface region.
 12. The method of claim 11, comprisingwherein the lattice matching atoms increase the second lattice constantb if the first lattice constant a is greater than the second latticeconstant b before the incorporation of the lattice matching atoms. 13.The method of claim 11, comprising wherein the lattice matching atomsdecrease the second lattice constant b if the first lattice constant ais less than the second lattice constant b before the incorporation ofthe lattice matching atoms.
 14. The method of claim 11, comprisingeffecting the momentary melting by irradiating the near-surface regionusing a laser.
 15. The method of claim 11, comprising melting thenear-surface region to a depth of between 0.3 μm and 1 μm.
 16. Themethod of claim 11, comprising wherein the implantation dose of thelattice matching atoms is in the range of 1×1015 cm-2 to 1×1016 cm-2.17. The method of claim 11, comprising performing, after the melting ofthe near-surface region, a non-melting thermal process at the substrate.18. The method of claim 17, comprising wherein the non-melting thermalprocess takes place before the epitaxial deposition of the layer. 19.The method of claim 17, comprising wherein the non-melting thermalprocess takes place after the epitaxial deposition of the layer.
 20. Themethod of claim 18, comprising producing, before the non-melting thermalprocess, a barrier layer on the near-surface region.
 21. The method ofclaim 20, comprising wherein the barrier layer is an oxide layer. 22.The method of claim 20, comprising again removing the barrier layerafter the non-melting thermal process.
 23. A method of making asemiconductor comprising: providing a monocrystalline substrate made ofa semiconductor material; and producing a monocrystalline layer having afirst lattice constant a on the monocrystalline substrate having asecond lattice constant b at least in a near-surface region, the secondlattice constant being different from the first lattice constant acomprising: implanting lattice matching atoms at least in thenear-surface region; momentary melting of the near-surface region; andepitaxial deposition of the layer on the near-surface region that hassolidified in monocrystalline fashion.
 24. The method of claim 23,comprising wherein the semiconductor material is silicon.
 25. The methodof claim 23, comprising repeating the implantation of lattice matchingatoms, the momentary melting and the epitaxial deposition of the layeronce or a number of times.